ec2 systemd unable to mount nfs on boot and it times out

Question

I'm running latest version of Red Hat Enterprise Linux Server release 7.0 (Maipo):

[root@ip-10-184-161-46 ~]# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 7.0 (Maipo)
[root@ip-10-184-161-46 ~]# rpm -q nfs-utils
nfs-utils-1.3.0-0.el7.x86_64
[root@ip-10-184-161-46 ~]# 

I have following entries inside of my /etc/fstab:

[root@ip-10-184-161-46 ~]# grep -v ^# /etc/fstab | tail -2
UUID=0f89adb9-ac88-4be5-b6cc-52a05bbdb825 /                       xfs     defaults        1 1
ip-10-164-175-246.ec2.internal:/var/www/html    /var/www/html/  nfs4    defaults    0   2
[root@ip-10-184-161-46 ~]# 

after instance's reboot, I saw following inside of rsyslog.service for systemd:

Jul 19 22:10:03 ip-10-184-161-46 systemd: Job ip\x2d10\x2d164\x2d175\x2d246.ec2.internal:-var-www-html.device/start timed out.
Jul 19 22:10:03 ip-10-184-161-46 systemd: Timed out waiting for device ip\x2d10\x2d164\x2d175\x2d246.ec2.internal:-var-www-html.device.
Jul 19 22:10:03 ip-10-184-161-46 systemd: Dependency failed for File System Check on /ip-10-164-175-246.ec2.internal:/var/www/html.
Jul 19 22:10:03 ip-10-184-161-46 systemd: Dependency failed for /var/www/html.
Jul 19 22:10:03 ip-10-184-161-46 systemd: Dependency failed for Remote File Systems.
Jul 19 22:10:03 ip-10-184-161-46 systemd: 
Jul 19 22:10:03 ip-10-184-161-46 systemd: 
Jul 19 22:10:03 ip-10-184-161-46 systemd: 
Jul 19 22:10:03 ip-10-184-161-46 systemd: 

manual way:

[root@ip-10-184-161-46 ~]# mount -a
[root@ip-10-184-161-46 ~]# echo $?
0
[root@ip-10-184-161-46 ~]# mount | grep '/var/www/html'
ip-10-164-175-246.ec2.internal:/var/www/html on /var/www/html type nfs4 (rw,relatime,vers=4.0,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,port=0,timeo=600,retrans=2,sec=sys,clientaddr=10.184.161.46,local_lock=none,addr=10.164.175.246)
[root@ip-10-184-161-46 ~]# 

nfs.service is running on another instance and uptime suggests that it didn't go down, so I'm trying to understand why systemd was not able to mount it upon boot (Timed out) yet trying to mount it manually was NOT an issue.

Any ideas why systemd couldn't mount it on boot?

Answer 1

It could be that it's trying to mount the device before it's brought eth0 up (and therefore has no network connection). You can fix this by simply appending _netdev to the options portion of the fstab (i.e; defaults,_netdev).

_netdev is a special flag which instructs the kernel that this is a network based device, so will not mount without a network connection. Therefore, upon bootup, it will mount all devices that do not have this flag, brings up the network connection (which almost always happens after the fact), then brings up _netdev devices.

Answer 2

... per redhat's 8.3. NFS Client Configuration

changing line from:

ip-10-146-180-60.ec2.internal:/var/www/html /var/www/html/  nfs4     defaults,_netdev   0   2

to:

ip-10-146-180-60.ec2.internal:/var/www/html /var/www/html/  nfs defaults    0   0

solved my issue.